Geographical variation in resource use by specialist versus generalist butterflyfishes

Keywords

Butterflyfishes

Abstract

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​Localised patterns of resource use can be constrained by multiple
factors. Comparison of resource use at multiple locations with differing
resource availability can allow fundamental specialists to be
distinguished from species that simply feed predominantly on prey types
that are locally abundant. This study investigates geographic variation
in the feeding ecology of coral-feeding butterflyfishes to examine
whether patterns of resource use and levels of dietary specialisation
vary among distinct locations, corresponding with changes in resource
availability. Our specific aims were to investigate whether the dietary
niche breadth of four butterflyfishes varies among five geographically
separated locations and assess whether each species utilises similar
resources in each location. Resource availability and dietary
composition of four butterflyfishes were quantified at three sites
across each of five geographic locations throughout the Pacific. Niche
breadth, niche overlap, and resource selection functions were calculated
for each species at each site and compared among locations.
Availability of dietary resources varied significantly among locations
and sites. Chaetodon vagabundus, C. citrinellus and C. lunulatus had low levels of dietary specialisation and used different resources in each location. Chaetodon trifascialis
had high levels of dietary specialisation and used the same few
resources in each location. Our results indicate that relative levels of
dietary specialisation among different butterflyfishes do hold at
larger spatial scales, however, geographical variation in the dietary
composition of all butterflyfishes indicates that prey availability has a
fundamental influence on dietary composition. Highly specialised
species such as C. trifascialis will be highly vulnerable to
coral loss as they appear to be largely inflexible in their dietary
composition. However, the increased feeding plasticity observed here for
C. trifascialis suggests this species may have a greater capacity to respond to coral loss than previously assumed.